The invention relates to a process and a device for carrying out the cutting of a multilayer assembly comprising a plurality of thin layers and consisting of an electrochemical generator in the form of thin layers or of a constituent part of such a generator, the multilayer assembly comprising at least one layer which consists of a metal ribbon or contains a macromolecular material.
A significant group of multilayer assemblies in the form of thin layers, which comprise at least one layer consisting of a metal ribbon or containing a macromolecular material, is that comprising electrochemical current generators in the form of thin layers, which generators may or may not be rechargeable, amongst which mention may be made of the electrochemical current generators which are described in the publication EP-A-0013199 and use a macromolecular material displaying ionic conduction and consisting of a solid solution of an ionisable alkali metal salt M.sup.+ X.sup.-, in particular a lithium salt, within a plastic polymer material consisting, at least in part, of one or more polymers and/or copolymers of monomers comprising at least one heteroatom, in particular oxygen or nitrogen, capable of forming bonds of the donor/acceptor type with the cation M.sup.+.
In their simplest structure, the electrochemical generators in the form of thin layers, as described above, are formed of an elementary multilayer assembly comprising a solid polymer electrolyte layer, comprising a macromolecular material displaying ionic conduction as mentioned above, inserted between a positive electrode layer, which may consist, in particular, of a mixture of a substance displaying electron conduction, such as carbon black, with various electrochemically active materials, and a negative electrode layer, formed, for example, from a ribbon of an alkali metal, in particular lithium, or an alloy based on an alkali metal, the elementary- assembly being arranged as a sandwich between two current collectors, which may be metal collectors or metallized plastic collectors. In certain configurations, the negative electrode consisting of a pure or alloyed alkali metal ribbon may itself be simultaneously the negative electrode and the corresponding current collector of the said elementary assembly.
In order to obtain generators of high energy capacity calling for relatively large surface areas, either flat stacks, or windings or various foldings of the elementary multilayer assembly are produced.
It is also possible to produce a base multilayer assembly comprising a layer of a metal of low ductility and, in this order and on the same side of the layer, a first positive electrode layer, a first solid polymer electrolyte layer, a negative electrode layer, a second solid polymer electrolyte layer, a second positive electrode layer and a peelable protective plastic film. By winding or folding the base multilayer assembly or by stacking such a multilayer assembly, after removing the peelable film, it is possible to obtain electrochemical generators of high energy capacities.
The electrochemical generators in the form of thin layers, which are subsequently subjected to the folding, winding or stacking operations in order to form generators of high energy capacity, may be assembled from the various layers, intended for forming them, taken separately, or from multilayer sub-assemblies already combining several of the constituent layers, these assembly operations being carried out continuously. In particular, it is possible to assemble the electrochemical generators in the form of thin layers as described in the publications FR-A-2616970 and FR-A-2616971.
Cutting operations are involved during the production of the electrochemical generators in the form of thin layers and these cutting operations may be carried out either on the complete electrochemical generators or on the constituent parts of the generators.
The cutting operations carried out making use of conventional cutting techniques by shearing with the aid of knives or by punching with a punch have various disadvantages. Firstly, the tool used always gives rise to strain at the point of cutting, which is reflected in time by a local deformation and therefore a significant risk of short-circuiting, with the consequence that cutting of the components must preferably be carried out before assembly of the generator. Moreover, the polymer materials and the metals, in particular alkali metals, which are involved in the composition of the components of the generators, lead to rapid fouling of the cutting tools, knives or punches. Finally, cutting may be carried out only in one direction if carried out in continuous operation. In the case of cutting in several directions, a complex movement either of the tool or of the multilayer assembly to be cut is required in order to carry out such an operation.
Moreover, the use of a cutting technique using a jet of water must be excluded taking account of the presence of alkali metal and in particular of lithium or of an alloy of such a metal in the negative electrode layer of the electrochemical generator.